The present invention pertains to a rivet fastener connection assembly consisting of a rivet casing and a rivet spindle employable in the rivet casing. The spindle has a bolt-shaped shaft and, a larger head unit compared to the diameter of the shaft, and the head unit is formed or set onto said shaft. A drilling unit is formed or set onto the head unit, where the rivet casing and has an inner thread over at least a part of its length, and the shaft of the rivet spindle has an outer thread corresponding to the inner thread, over at least a part of its length, and wherein means are provided on the rivet casing and/or on a contact flange formed on the rivet casing, for form- and/or force-fitted mount of the rivet casing against the workpiece to be riveted, and/or against a setting tool for the rivet connector.
This type of a rivet connector is known from DE-OS 17 75 430 or from U.S. Pat. No. 3,453,927. This rivet connector does not generate a rivet connection by pulling the rivet spindle out in an axial direction after inserting the rivet connector into a drilled hole in the workpiece, in order to deform the rearward, free end of the rivet casing by this process, but rather, it concerns a means of effecting the riveting itself by turning the rivet spindle. In this case, the rivet casing has an inner thread and the rivet spindle has an outer thread corresponding to the inner thread, and the tensile force to deform the free end of the rivet casing is exerted on the head unit by twisting the rivet spindle in the rivet casing. In this case, very strong friction forces will be generated since a deformation of the free end of the rivet casing will occur. Thus in this known rivet connector the rivet spindle will often break (for example, at a set breakpoint), so that the setting process of the rivet connection cannot be terminated at all.
DE 32 17 065 A1 discloses a method to gap-open the free-end region of the rivet casing of pull-rivets, where the pull spindle is pulled out only in an axial direction. Due to the special formation of the head unit on the pull spindle, a tear-off of the free end of the rivet casing is effected by pyramid-shaped beveling, whereupon the pyramid edges notch in the rivet casing, so that the rivet casing tears open axially when tightening the head. This type of the connector can only be used on pure pull-spindles, since these tear-open edges on the pull spindle would prevent a twist motion of the pull spindle against the rivet housing. In addition, when meshing with the rivet casing, the edges would immediately cause such a large rise in the torque that the rivet casing would also turn or twist in a radial direction. An orderly setting process thus could not be implemented.
From DE-AS 14 75 216 a rivet connector is known where the rivet casing is equipped with an inner thread and the rivet spindle is provided in an outer thread, so that by turning motion of the rivet spindle, the riveting can be completed. In this known rivet connection there are problems however, inasmuch as the turning of the rivet casing during tightening of the rivet spindle cannot be prevented, so that not only could the workpiece be damaged, but also the rivet itself will not sufficiently ensure reliability.
From DE-OS 19 63 526 a self-drilling blind rivet is known that has a thickened section at the region adjoining the head unit of the shaft of the rivet spindle, whereby a thread is cut into this thickening. This thickened section with thread has a diameter that is much larger than that of the rivet spindle itself, and during the setting process, through rapid tightening of the rivet spindle with this threaded region, an expansion of the rivet casing will be effected. Since the advance of the pull part is much larger for this rivet spindle than the thread pitch on the rivet spindle, this threaded section on the rivet spindle will merely be contracted into the rivet casing, without requiring an opposing thread to be formed in the rivet casing. Thus only the inside diameter of the rivet casing will be expanded, so that it will press against the wall of the drilled hole in the workpiece.
Finally, DE 32 46 625 A1 and from DE 35 42 581 A1, rivet connectors without a drill section are known, where the rivet casing is not deformed during the setting procedure, but rather the diameter of an additional casing located over the rivet spindle is expanded by means of the rivet casing.